Electric plug



p 2 1958 E. H. TERLINDE 2,850,711

' ELECTRIC PLUG Filed May 19, 1955 INVENTOR E7 9 Edward H. ref/ma BY @wma ATTORNEY United States Patent 1 2,850,711 ELECTRIC PLUG Edward H. Terlinde, St. Paul, Minn. Application May 19, 1955, Serial No. 509,624 7 Claims. (Cl. 33962) This invention relates to an improvement in electric plugs and deals particularly with a simple and effective plug which will effectively remain in position.

One of the difficulties often experienced with plugs of the type commonly used in electric receptacles lies in the difficulty which is often experienced in keeping the plug in place. The plugs are usually equipped with generally parallel prongs and the sockets usually include spring blades against which these prongs engage. The prongs are held in place merely by the frictional engagement between the prongs and the springs. In many instances this friction is not suflicient to hold the plug in the socket if there is any material pull upon the cord. An object of the present invention lies in the provision of a plug which is constructed so that it will remain engaged in the socket under normal stresses which might be provided thereupon. The arrangement is such that the plug must normally be engaged with the fingers if it is to be removed from its socket.

A feature of the present invention resides in the fact that, if desired, the plug may be actually locked in place in the socket. Sockets are usually made with the spring contacts enclosed within a plastic housing. This housing is usually provided with spaced slots into which the prongs may extend. If desired, the plug may be so arranged as to lock in this casing so that it cannot be removed except by manual manipulation.

A further feature of the present invention resides in the provision of a plug in which the contact prongs are resiliently supported. Portions of the prongs are normally out of parallel relation. The prongs may be turned into parallel relation by proper operation of the plug body. Thus the prongs may be bent parallel for insertion or removal of the prongs into the cooperative socket.

These and other objects and novel features of my invention will be more clearly and fully set forth in the following specification and claims.

In the drawings forming a part of the specification:

Figure 1 is a top plan view of a plug showing the construction thereof.

Figure 2 is an end elevation view of the plug shown in Figure 1.

Figure 3 is a perspective view showing the plug in posi tion for insertion into a socket.

Figure 4 is a plan view of a modified form of plug.

Figure 5 is a plan View of a modified form of plug construction.

Figure 6 is an end view of the plug shown in Figure 5.

Figure 7 is a side elevational view of the plug shown in Figures 5 and 6.

Figure 8 is a sectional view showing the manner in which the plug may lock into a socket of conventional form.

Figure 9 is a perspective view of another modified form of plug construction.

The plug may be formed in several difierent ways, each of which has its advantages and disadvantages. In other words, the various forms of construction are not believed entirely equivalent but have certain features in common.

With reference first to the structure shown in Figure l of the drawings, this figure illustrates a plug body 10 made of resilient material such as rubber or a resilient substitute. Into this body 10 is molded a pair of prongs 11 and 12, these prongs being connected to conductors 13 and 14. The major portion of these conductors are insulated as indicated at 15 and 16, respectively, and are enclosed in a cable 17 in the usual manner. In other words, the structure is very similar to the molded plugs which have been produced for some years, but in the present case it is essential that the bodies be cast of resilient material.

As indicated in the drawings, the plug body is provided with a generally V-shaped notch or groove 19 in one surface thereof. This groove 19 extends longitudinally of the body 10 between the prongs 11 and 12 and divides the upper portion of the body particularly at the extremity thereof. The groove is of sufficient depth to permit the flexing of the body 10 in a manner which will be later described in detail.

As is indicated in Figure 2 of the drawings, the prongs 11 and 12 are arranged with their fiat surfaces on planes which intersect at an acute angle. As viewed in Figure 2 0f the drawings, the lower edges 20 of the prongs are spaced apart a distance substantiallyless than the upper edges 21 thereof. The upper surface of the body 10 includes the notch 19. As is indicated in Figure 2, the walls 22 and 23 of the notch 19 may be substantially parallel to the flat surfaces of the prongs 11 and 12, re-

' spectively.

The purpose of this arrangement is to-provide a structure in which the prongs have fiat surfaces which are normally out of parallel relation but which can be flexed into parallel relation by a squeezing action on opposite sides of the plug body. In other words, by grasping the plug between the thumb and fingers so that the sides 24 and 25 may be subjected to inward pressure, the body of the plug will compress together on opposite sides of the notch 19 so that the walls 22 and 23 of the notch may virtually come into contacting relation, as is indicated in Figure 3. Thus by squeezing the walls of the plug the prongs may be swung into parallel relation so that they will readily fit into a socket of conventional design.

If it is preferred, the prongs may remain full and unbroken and the release of the squeezing pressure against the sides of the plug will cause these prongs to tend to return to their normal angular relation as indicated in Figures 1 and 2. This will cause a binding action against the walls of the slots of the socket into which the prongs are inserted. As a result, the plug will be securely anchored in the socket by friction but will release if sufficient pulling pressure is applied. The pressure necessary to release the plug is substantially greater than is usually experienced.

If it is desired, the plug may be actually locked in its socket. This is accomplished by providing notches 26 and 27 in the upper edges of the prongs 11 and 12 (as viewed in Figure 1) at a point adjoining the end of the plug body 10. When the prongs are notched in this manner, they are not prevented from twisting by the walls of the slots such as 29 and 30 in the socket receptacle 31, and, therefore, after the plug is inserted the prongs will assume their natural angular relation as is indicated in Figure 8. This is true because the notches 26 and 27 embrace the walls of the slots 29 and 30. When the prongs have twisted into the position shown in Figure 8, they remain firmly against the spring contacts 32 and 33 within the plug and at the same time the outer edges of the notches form shoulders to prevent withdrawal of the prongs from the socket. Thus the plug cannot be removed by a longitudinal pull.

When the plug is to be removed from the socket the body of the plug is subjected to a squeezing pressure to close the notch 19 and to swing the prongs into, or toward, parallel relation. When they have been sufficiently twisted, they may be withdrawn from the socket housing with no difliculty.

In Figure 4 of the drawings I disclose a modified form of construction. In this arrangement the plug body 34 is bifurcated at the extremity from which the prongs extend. In' other words, the body 34 includes a central notch or slot 35 which separates the body-into two.

to a cable 43. As is shown in the drawings the prongs 39 and 40 normally diverge apart as indicated in Figure 4 of the drawings so' that they are out of parallel relation. However, as the body 34 is formed of rubber or other suitable or similar resilient material, the projections may be flexed together to bring the prongs into parallel relation. In this position they may be inserted or removed from the socket.

.It will be obvious that when the plug is to be inserted, the projections are flexed together until the prongs are parallel and the prongs may then be inserted into the socket body. When the prongs are in place the squeezing pressure on the plug body is released permitting the prongs to swing toward diverging position. This greatly increases the frictional engagement of the prongs in the socket and tends to prevent withdrawal of the plug.

In Figures 5 and 6 and 7 of the drawings, I disclose another modified form of constructionof plug. In this device the plug is provided with a plug body 44 of resilicut material having prongs 45 and 46 projecting therefrom. These prongs are connected to conductors 47 and 49 which lead to the cable 50.

In the particular construction illustrated, the prongs are provided with neck portions 51 and 52 'of reduced a plug body is formed of material which is sumciently resilient to permit the prongs to twist until the normally angular ends are substantially parallel. In other words,

the pointed ends act as cams to twist the prongs until they are engaged in the socket and will slip through the a socket slots. As the prongs are further inserted, the

' prongs arepermitted to' twist back into their normal angularrelation by the engagement of the'reduced width or neck portions 51 and 52 of the prongs with the socket slots. 7

The removal of the plug is the reverse action of. that described. As is indicated in Figure 7 of the drawings, the prongs are provided with inclined or diverging edges adjoining the neck portions 53 and 52. These diverging edges 55 again act as cam 'surfacesto twist the prongs into generally parallel relation as the plug is pulled from the socket.

In Figure 9 another slightly modified form of con struction is illustrated. In this figure is illustrated a plug 56 having a body formed of two sections 57' and 59 which are attached together in any suitable way such as by bolts 60. In the body of the plug and between the sections are provided'two elongated inserts 61' and 62 of resilient material such as rubber. These inserts are preferably provided with anchoring end portions 63 and 64 which are rectangular in cross-section or otherwise shaped to prevent rotation of this end of the insert. The resilient plugs act to embedportions of prongs 65 i and 66.

The prongs 65 and 66 are preferably twisted. The tapered ends of the prongs are, generally parallel, while the planes of the surfaces of the prongs are diverging, at points spaced from the ends. The prongs also are narrower in width adjoining the portions embedded in the inserts 6'1 and 62.

The prongs are spaced to enter the slots of a plug socket. As the prongs are pushed inwardly, the shape of the prongs causesthernto twist, twisting the outer ends of the inserts, When the 'narrower prong ends enter the socket slots, the prongs may twist back toward their normal position, creating a resistance to removal'of the prongs.

. Thus it'will be seen that by resiliently supporting the prongs of the plugs -they'may engage in the sockets with substantially more friction than would otherwise be normally obtainable. Either the prongs may be manually moved into substantially parallel relation by a squeezing action on the body of the plug, or else the' prongs are so shaped as to twist in the plug body, the body being sufliciently resilient to permit such action.

' In accordance with the patent statutes, I have described the principles of construction and operation of my electric plug',"and while I have endeavored to set forth the best embodiment thereof, I desire to have it understood that obvious'changes may be made within the scope. of the following claims without. departing from the spirit of my invention. i

i I claim l. A' plug including a'body of resilient material, a

pair of elongated stripsforming prongs partially embedded in s aid body and projecting parallel therefrom in the same direction from said body, the flat surface of said prongs being arranged on planes intersecting at an acute angle, said body having a notch therein between said prongs, said .notch eXtending longitudinaliy of said prongs, said body being flexible under compression transversely of said notch to move the walls of the notch together, the compression of said body to bring the notch walls together acting to twist said prongs toward parailcl relation.

' 2. The construction described in claim-1 and in which said prongs include neck portions of reduced width adjoining said body. 7

3. A plug comprisinga plug body of resilient material, a pair of prongs extending parallel and in the same'general direction from said plug body and partially embedded thereimconductors connected to the embedded portions of said prongs, said prongs comprising strip members having flat surfaces arranged on planes intersecting at an acute angle, said body having an elongated notch therein betweenjt he edges of the prongs which are farthest apart, flexing of said body transversely of said prongs ast nsto par i lly clo e s id n t h' nd t wis the planes of said prongs toward parallel relation, said prongs having HQi QS' in :thQ .edgcs thereof most widely spaced apart.

4. The construction described in claim 3 wherein the notches in the edges. of the prongs which are farthest apart, are .uearqthe point where said prongs become embedded in said plug body. f

5; The construction described in claim 3 and in which said notch is generally V-shaped in cross section.

6. The construction described in claim 3 and in which said notch is generally V-shaped in plan with the apex of the V near theend of the plug body opposite the end from which the prongs project. '7; The construction described in claim 3 and in which said notch is generally V-shaped in cross section and in plan with the apex ofthe V near the end of the plug bodyopposite that from which the prongs project.

Referenees Cited in the file of this patent i 

